Monitoring resource usage

My recent use of my Current Cost unit to determine whether or not the insulation on my heat store was efficient enough has rekindled my interest in energy monitoring again. And the fact that my gas-powered central heating boiler has broken down made me wonder how hard it would be to measure the gas consumption of my house in the same way that I currently measure my electricity consumption. And if I’m going to do that, then I may as well look at the water usage too. And it may be interesting to combine those with the internal and external temperature.

Since I started playing with my Current Cost, back in 2007, it has become a Current Cost Classic, and there is a new kid in town, the Current Cost Envi, which does everything the Classic does, but has the ability to also independently monitor several individual appliances. It occurred to me that it would be possible to subvert a couple of those appliance monitors to measure the gas and water usage. I suspect that this is likely to confuse the Envi display unit (which will assume that all inputs are electrical) but the XML that comes out the unit and into my home server will allow me to correctly interpret the data and present it as a series of useful graphs.

So on Thursday I acquired a shiny new Current Cost Envi unit in ghastly white, as sadly my supplier didn’t have any tasteful black ones left. I also had a chat with the friendly folks at Current Cost, and thanks in part to the long relationship that we’ve had with them, I’ve acquired a couple of wireless sensor development boards. These have a single simple digital input, which sends a fixed 0 or 500 signal to the display unit on it’s own channel. Not quite as useful as a proper analog setup (which I’m already thinking I could obtain by hacking a current-clamp board!), but absolutely ideal for counting pulses on (say) a gas or water meter…

So the next part of this project is to dust off my (ancient) electronics skills, and work out how to interface one of these boards to my gas meter in such a way that the gas board won’t have kittens next time they read the meter; ie, contactlessly. A few people have already done this, using a variety of different mechanisms, depending on their meter type. I need to spend some time with my gas meter to determine what’s possible, but hopefully I can do something simple with hall-effect sensors, photodiodes or similar.

Water is looking more difficult; I’ll have to buy and install my own flow-meter into the rising main of the house; not sure how expensive that will work out to be, or how I could calibrate it, but I’m sure there must be suppliers out there with lots of information waiting to be read on the internet.

And if nothing else, that would finally settle the discussion over whether it will be cheaper for me to move to a water meter tariff or not!

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